200 
IlERAMIC STUDIO 
POTTERY CLASS 
ONE PART MOLD 
Fred H. RhcaJ 
CONVERSATION and correspondence with followers 
of the pottery class have led me to believe that one 
or two articles on moldmaking would not be wasted. It 
has been pointed out, and it is quite obvious, that the 
more delicate type of pottery can be made only by means 
of molds, or by throwing and turning. 
While some studio potteries have made beautifully 
finished built pottery, this method demands extraordinary 
skill and patience, if for lightness and finish, it is to be 
compared to the most ordinary pot cast in a mold made 
by the merest amateur. Throwing and turning is out of 
the question except for those who have money and time, 
but any amateur may with little experience, and without 
an expensive outfit, make practical molds of any ordinary 
pottery shape. I am writing for those who are entirely 
unfamiliar with this work, if you like, for those who do 
not know how to mix plaster. 
No special studio will be needed, and no tools or out- 
fit will be used which cannot readily be obtained at small 
cost. 
I will deal with the one part mold, giving the con- 
struction of the shape which may be made in such a mold, 
and then showing how both the model and mold is made. 
SHAPE CONSTRUCTION — ONE PART MOLD. 
Obviously, a one part mold is a mold in one piece 
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from which the cast or pressed pottery will "draw" with- 
out mutilation to the mold or the pottery. 
With the exception of the cylindrical shape, and not 
considering the possible variations on this construction, 
the only type of shape which may be made in a one part 
mold is the shape having a contour which gradually decreases 
in radius from the top to the base. For example, in figure 
one, shape one is cylindrical and figures two, three and four 
gradually decrease in radius from the top to the base, con- 
sequently the shape when it has dried sufficiently must 
readily draw or slide from the mold. 
In figure four I give varieties of shapes one, two, three 
and four. In every instance the principle governing the 
shape construction for a one part mold is violated by 
narrowing the top of the shape, thus making it impossible 
to make the mold in less than two pieces, one upper and 
one lower part. The dotted lines mark the seam or point 
of contact between the two parts. 
In figure two I show a development of shapes one, 
two, three and four. In every instance the shape grad- 
ually decreases in radius from the top to the base, conse- 
quently these shapes may all be made in one piece molds. 
These constructions may be varied and the develop- 
ments elaborated, but the designer must be careful not to 
diminish the size of the base to too great an extent. 
In figure five I give developments of figure two, show- 
ing, by merely widening the base, shapes which would re- 
quire a three part mold consisting of two side pieces and 
a base. I will discuss these later, but it is necessary to 
mention them now in order to give the student some idea 
of the shape construction, and to make this understanding 
doubly clear I give a simple chart (figure 7) giving the 
principal construction of those shapes which may be made 
in one piece. 
The Model. 
The model from which the molds are made may be 
executed in clay, plaster, wood, glue, or any other sub- 
stance which can be separated without injury to the mold. 
As the molds are made from plaster, and as the plaster 
model is easy to make, there is no necessity for describing 
any other process. I will call the process under dis- 
cussion the axle and profile method because the setting 
or hardening plaster is smeared on an axle which is made 
to revolve against a zinc profile which cuts and forms the 
plaster to the desired shape. 
Figure three shows a skeleton bench (sketch 1) across 
which lies a steel rod or axle (sketch 4) in a socket (sketch 
7) at each end. The top portion of both sockets can 
readily be unscrewed in order that the axle may be lifted 
off the bench and the model removed when it is finished. 
A dirk or wheel with a handle (sketch 8) fitted to 
one end of the axle to facilitate the turning of the axle 
while the model is 'being formed. No. three is a board 
on which the profile (sketch 2) is nailed. Sketch six is a 
bowl for plaster. Sketch five is the model and sketch 
2 A is another profile showing about the amount of metal 
in proportion to the shape. The bench may be of any 
size. The measurement of the inside of the top of the 
frame will determine the size of the largest model which 
may be made. Few students would need a frame hav- 
ing a larger inside measurement than 14" x 14". A bench 
of this size would make arnodel twelve inches high and 
wide, and^such a^bench~would take up little room in the 
studio; it need stand "only^eight inches high and when in 
uuse it cold be placed on the work table. 
